GitLab

This CL switches to use xenial for test as many as possible.

Sheriff:
If this broke some ci/fyi builder, feel free to revert this.

TBR=jbudorick

Bug: 954450
Change-Id: I98abfb50bb10ca3eeec0e23d197fe7672c8acc95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1689513Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#675527}